The aim of these investigations is to clarify the role of the platelet and of the macrophage in the process of wound repair and granulomatous inflammation. These studies will: Isolate, purify, and characterize the factor released from macrophages that stimulate fibroblast proliferation; examine how the macrophage promotes in fibroblast migration and proliferation in cell culture and study the role of the platelet factor in fibroblast migration in cell culture; determine whether the presence of platelets in healing wounds is required for initiation of fibroblast migration and proliferation during the process of wound repair in vivo; determine the role of platelet factors and macrophage derived factors in stimulating epithelial migration and proliferation in cell culture and in in vivo wound repair; assess the role and importance of macrophage factors in promoting the continued fibroplasia seen in chronic granulomatous reactions.